Currently, the electrophotographic technology is widely applied for copying machines, laser beam printers, fax machines or the like because of its high-speed processability, high image quality and so on.
As electrophotographic photosensitive bodies in the field of this electrophotographic technology, inorganic photoconductive substances such as selenium, selenium/tellurium alloys, selenium/arsenic alloys, cadmium sulfide or the like have mainly been used conventionally. However, recently an electrophotographic photosensitive body using an organic photoconductive substance has been developed from the viewpoint of toxicity, safety, cost, productivity and the like. When the organic photoconductive substance is a low-molecular weight substance, it is a general practice to mix it with a binder resin to form a coating film.
As the binder resin, various thermoplastic resins and thermosetting resins such as polymethylmethacrylate, polystyrene, vinyl polymers such as polyvinyl chloride and copolymers thereof, polycarbonate, polyester, polysulfon, phenoxyresins, epoxyresins and silicone resins have been used. Of these various resins, a polycarbonate resin shows relatively excellent characteristics and hence is used popularly.
Uses of various polycarbonate resins have been reported. For example, Patent Document 1 teaches to use a polycarbonate resin derived from 1,1-bis(4-hydroxyphenyl)cyclohexane and Patent Document 2 teaches to use a polycarbonate resin derived from 2,2-bis(4-hydroxyphenyl)propane, as a binder resin respectively.
Among the electrophotographic photosensitive bodies using these known organic photoconductive substances and various binder resins, ones comparable to an electrophotographic photosensitive body using an inorganic photoconductive substance in terms of sensitivity and so on are obtained.
These organic electrophotographic photosensitive bodies can be formed into a thin film with ease by means of a cast film-forming method and hence are suitable for mass production and the prices are relatively low. However, though having these excellent properties, the organic electrophotographic photosensitive body does not necessarily have satisfactory wear resistance, and hence an improvement is required.
For the purpose of improving wear resistance, several additives are proposed. For example, Patent Document 3 teaches silicone oil and an example of Patent Document 4 teaches perfluoroalkylacrylate.
In Patent Document 3, silicone oil compatible with a constituent material of the photosensitive layer of the electrophotographic photosensitive body is added by an amount exceeding the compatible limit with the constituent material of the photosensitive layer. Since an extremely large quantity of silicone oil is used, silicone oil is separated out within the layer. Therefore, there is a severe constraint between the size of a particle or a liquid droplet and the thickness of the layer to be added.
In Patent Document 4, perfluoroalkylacrylate is added at the time of forming a charge transport layer of the electrophotographic photosensitive body in Example 5. However, since 1 part of perfluoroalkylacrylate based upon 4 parts of a binder resin, which is a large amount, is added, there is a concern about keeping of transparency.
Patent Document 1: Jpn. Pat. Laid-Open Publication No. S60-172044
Patent Document 2: Jpn. Pat. Laid-Open Publication No. S63-170647
Patent Document 3: Jpn. Pat. Laid-Open Publication No. H10-171135
Patent Document 4: Jpn. Pat. Laid-Open Publication No. 2002-268241